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The Southland Corporation March 31, 1998 <br /> Store 19976,Manteca, CA _ Page 2 <br /> BACKGROUND <br /> In September of 1996, three 10,000-gallon underground storage tanks and associated fuel dispensing <br /> equipment(pump islands and fuel lines)were removed from the site (refer to Fluor Daniel GTI's Underground <br /> Storage Tank Removal Summary, dated October 16, 1996, for further information). Soil samples collected <br /> from the base and sidewalls of the tank excavation-at depths of 13-15 feet below grade were analyzed for total <br /> i petroleum hydrocarbons as gasoline(TPHg) and benzene,toluene, ethylbenzene,total xylenes, and methyl <br /> tertiary butyl ether(MTBE)by EPA Method 8015/8020. The sample containing the highest MTBE concentration <br /> as detected by EPA Method 8020 was also analyzed by EPA Method 8260 for MTBE. Each soil sample was <br /> also analyzed for total lead using EPA Method 6010. All sampling locations and analyses were as requested <br /> by the SJCDEH and the City of Manteca Fire Department, and the sampling was witnessed by representatives <br /> of both these agencies. Analytical results indicated that the highest soil hydrocarbon concentrations of 0.93 <br /> f ppm benzene and 220 ppm TPHg were present beneath the southern end of the eastern-most underground <br /> storage tank. The highest concentrations of MTBE as measured by EPA Method 8260 (0.35 ppm) were <br /> observed beneath the northern end of the western-most underground storage tank. Total lead concentrations <br /> ranged up to 17 ppm, which are within background conditions. See Figure 2 for former and current tank <br /> ..locations and a summary of previous soil analytical results. <br /> SUMMARY OF GEOLOGY <br /> Soil types encountered during underground storage tank removal consisted of interbedded silty sand to about <br /> 1,0 feet below grade, underlain by silty clay with interbedded sand to about 15 feet below grade. <br /> Groundwater was not encountered during previous field activities. <br /> PROPOSED SCOPE OF WORK <br /> t k <br /> Purpose <br /> The purpose of the work is to delineate the lateral and vertical extent of the soil hydrocarbon plume, and to <br /> evaluate groundwater conditions beneath the.site. <br /> If additional data substantiates that: 1)residual hydrocarbon levels are the same or lower than those previously <br /> encountered and/or 2)low risk-groundwater conditions apply(i.e.the plume is relatively small,delineated, and <br /> there are no shallow domestic or muncipal wells within 2,000 feet of the site), site closure will be requested. <br /> FLUOR DANIEL GTI <br /> f <br />